The present invention relates to a wafer mapping apparatus which is configured to recognize semiconductor wafers (hereinafter simply referred to as wafers) stored in a container which is to be conveyed to a load port, and relates also to a load port including the wafer mapping apparatus.
In a semiconductor manufacturing process, a container storing wafers from which semiconductor devices are manufactured is conveyed to a load port which is provided at an entrance of a processing room which is a clean environment therein, and after a door of the load port is opened, the wafers stored in the container are taken into the processing room by a robot or the like. In the container, the wafers are placed on vertically-aligned shelves in the container.
Wafer size has recently increased in accordance with the increased production of semiconductors, and wafers which are 450 mm in diameter will be in use. Currently-popular large wafers which are 300 mm in diameter are stored in a sealed container termed a FOUP (Front Open Unified Pod) and conveyed to a load port. A front opening of the sealed container is connected with an entrance of a processing room in a sealed condition. A lid of the container is opened together with a door of the load port, and the wafers are taken into the processing room (see e.g., Patent Literatures 1 to 3 (Patent Literature 1: Japanese Patent No. 4246420, Patent Literature 2: Japanese Patent No. 4501755, and Patent Literature 3: Japanese Patent No. 4866315)). Previously-popular small wafers which are, for example, 200 mm in diameter are typically stored in an open container termed an open cassette and conveyed, and are taken into a processing room through a load port, in a clean room (see e.g., Patent Literature 4 (Patent Literature 4: Japanese Patent No. 4096213)).
When wafers are taken from a container such as the FOUP and the open cassette described above into a processing room, a wafer mapping apparatus which maps and recognizes the state of the wafers in the container is used, in order to allow a robot or the like to automatically take the wafers. The wafer mapping apparatus is arranged in such a way that, a transmission optical sensor having a horizontally-extending optical axis is, as a mapping sensor, attached to a leading end portion of a mapping device such as a mapping arm and a mapping frame, which device is movable forward, backward, upward, and downward. After the mapping device is moved forward to insert the mapping sensor into the front opening of the container, the mapping sensor is moved in an up-down direction in the container. In this way, the wafer mapping apparatus detects the wafers stored in vertically-aligned shelves. The mapping device is attached to a moving mechanism which is able to linearly move in an up-down direction. As this linear moving mechanism, an elevatable door of a load port may be used.
Such a wafer mapping apparatus is provided with a protrusion sensor which detects a wafer which protrudes forward from the back side of a shelf, in order to prevent in advance of the collision of the wafer with the mapping sensor which moves in the up-down direction in the container (see e.g., Patent Literatures 1 to 4). As the protrusion sensor, Patent Literature 1 recites a transmission optical sensor which is attached to the fixed frame of the door of the load port so that the optical axis of the sensor extends in the up-down direction. As the protrusion sensor, furthermore, Patent Literature 2 recites two transmission optical sensors which are attached to a mapping frame which is movable in the up-down direction so that the optical axis of each sensor extends in the up-down direction, whereas Patent Literature 4 recites a transmission optical sensor which is attached to a mapping arm so that the optical axis of the sensor horizontally extends. Furthermore, Patent Literature 3 recites that, as a first protrusion sensor, a transmission optical sensor is attached to the fixed frame of the door of the load port so that the optical axis of the sensor extends in the up-down direction, and as a second protrusion sensor, a transmission optical sensor is attached to a mapping arm to have a horizontally-extending optical axis. This second protrusion sensor is provided not for preventing the collision of the wafer with the mapping sensor. This sensor is an intermediate sensor for detecting misregistration of wafers which are taken by a robot or the like.
In the meanwhile, it has been demanded to modify a load port which deals with currently-popular wafers stored in a FOUP and 300 mm in diameter to be able to deal with wafers stored in an open cassette and 200 mm in diameter. In response to such demand, there is a proposal that a closed cassette adopter is provided to cover the outside of an open cassette for wafers with 200 mm diameter, the cassette adopter is attached to a load port for wafers with 300 mm diameter, and the wafers with 200 mm diameter stored in the open cassette are taken into a processing room in a sealed condition. To put it differently, the cassette adopter and the FOUP for 300-mm wafers are positioned at the same position and connected with the entrance of the processing room in a sealed condition, and the 200-mm wafers stored in the open cassette and the 300-mm wafers stored in the FOUP are taken into the processing room by a shared robot or the like (see e.g., Patent Literature 5 (Japanese Unexamined Patent Publication No. 2012-64827)).